In a paper by L. Moller, "An Optical CDMA Method Based on Periodic Spectrum Encoding", presented at the Thirteenth Annual Conference on European Fibre Optic Communications and Networks, Brighton, England, 1995, pp. 178-181, an asynchronous transmission system is described which uses a CDMA (code-division multiple access) method based on periodic spectrum encoding. In that system, the code words used for gaining access are implemented by different transfer functions of periodic filters. The method uses a particular periodic spectral filtering technique for broadband optical signal sources. An information signal can be received and processed in a receiver only if the periodicities of the filter transfer functions of the transmitter and receiver match.
In the communications system described, crosstalk occurs when two or more transmitters with filter transfer functions that are contiguous to each other in the tuning range are transmitting simultaneously.